Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session P16: Multi-mode and 3D-Cavity Circuit QED Systems I |
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Sponsoring Units: DQI Chair: Bruno Taketani, Univ Federal de Santa Catarina Room: 201 |
Wednesday, March 4, 2020 2:30PM - 2:42PM |
P16.00001: Implementation of a multi-mode qubit in coaxial circuit QED: Part 1 Sophia Sosnina, James Wills, Simone D Fasciati, Salha Jebari, Giulio Campanaro, Shuxiang Cao, Peter Spring, Takahiro Tsunoda, Ian Yang, Peter J Leek, Brian Vlastakis Alternative qubit design is an active field of research in superconducting quantum systems. In particular, multi-mode quantum circuits can allow error-protected subspaces, nonlinear coupling for multi-qubit operations, and additional mechanisms for state readout or control. In this talk we introduce a simple multi-mode coaxial transmon qubit - a two-mode qubit with a dipole-like differential mode and a coaxial common mode. We discuss the qubit Hamiltonian, analyze its sensitivity to fabrication imperfections, and discuss the effects of quasi-particle tunnelling in this system. Finally, we consider extensions of the design to multi-qubit settings. |
Wednesday, March 4, 2020 2:42PM - 2:54PM |
P16.00002: Implementation of a multi-mode qubit in coaxial circuit QED: Part 2 James Wills, Sophia Sosnina, Simone D Fasciati, Salha Jebari, Giulio Campanaro, Shuxiang Cao, Peter Spring, Takahiro Tsunoda, Ian Yang, Peter J Leek, Brian Vlastakis We discuss experimental results on a multi-mode qubit operating within a coaxial circuit QED architecture. This device includes a two-mode coaxial transmon qubit with out-of-plane coupling to a coaxial LC resonator. We discuss the characterisation of devices using two-tone spectroscopy and coherence measurements. We observe a strong cross-Kerr coupling between the differential and common modes of the qubit, which results in a qutrit-like behavior. Finally, we investigate charge sensitivity in such a device, and discuss its potential as a novel probe of charge fluctuations in superconducting quantum systems. |
Wednesday, March 4, 2020 2:54PM - 3:06PM |
P16.00003: Chiral cavity quantum electrodynamics in a 3D microwave lattice coupled to a transmon qubit (Part 1) Margaret Panetta, Clai Owens, Srivatsan Chakram, Brendan Saxberg, Gabrielle Roberts, Ruichao Ma, Jonathan Simon, David I Schuster Recent advancements in the ability to create and manipulate superconducting quantum systems have created an exciting opportunity to construct from the ground up quantum materials tailored to host rich interactions. We have designed a two-dimensional meta-material in which microwave photons inhabiting a lattice of superconducting 3D microwave cavities interact strongly with ferrimagnets, realizing a quarter-flux Hofstadter model for light. We perform state tomography on the lattice and demonstrate chiral, time-reversal symmetry broken edge transport with lifetimes ~1000 times larger than the site to site tunneling rate. This is the first photonic topological lattice platform compatible with strong interactions. We have coupled a single transmon qubit to this lattice, enabling this platform to study chiral cavity quantum electrodynamics. Here we discuss the design and testing of this system and describe prospects for its application. |
Wednesday, March 4, 2020 3:06PM - 3:18PM |
P16.00004: Chiral cavity quantum electrodynamics in a 3D microwave lattice coupled to a transmon qubit (Part 2) Clai Owens, Margaret Panetta, Srivatsan Chakram, Brendan Saxberg, Gabrielle Roberts, Jonathan Simon, David I Schuster We have previously realized a chiral meta-material for microwave photons. We now describe our work combining a single transmon with this topological lattice, achieving, for the first time, a platform for chiral cavity quantum electrodynamics. We show strong coupling between the qubit and the topological lattice. Using the qubit we prepare arbitrary quantum states of the lattice edge modes and we can non-destructively measure their photon occupation. Finally, we describe a path towards coupling a transmon to each site of the lattice, enabling exploration of a Harper-Hubbard model which is anticipated to support fractional Chern insulating many-body phases. |
Wednesday, March 4, 2020 3:18PM - 3:30PM |
P16.00005: Driving a Dark State Qubit in 3D Waveguide QED Maximilian Zanner, Christian M. F. Schneider, Mathieu L. Juan, Oscar Gargiulo, Stefan Oleschko, Aleksei Sharafiev, Gerhard Kirchmair The collective behavior of coupled qubits in a waveguide leads to sub-radiant and superradiant states. This effect was extensively studied theoretically and experimentally over the last decade. The appearing dark states can be used to generate an effective two level system that has longer coherence times than a single qubit in the same physical configuration. We engineered a system that creates subradiant and superradiant states by using a direct dipole-dipole, as well as a waveguide-mediated interaction. We show experimentally that this two-qubit dark-state can be used as a qubit state even though it is embedded in an open system. Furthermore, we use the bright state to read out the qubit encoded in the dark state. |
Wednesday, March 4, 2020 3:30PM - 3:42PM |
P16.00006: Universal control of superconducting cavities with weak nonlinearity Alec Eickbusch, Salvatore S Elder, Phillipe Campagne-Ibarcq, Zhenghao Ding, Shantanu Jha, Nicholas Frattini, Christa Flühmann, Luigi Frunzio, Robert Schoelkopf, Michel H. Devoret In superconducting cavities, fast universal control usually requires an inherited Kerr nonlinearity on the order of a few kHz. However, in many bosonic quantum error correction codes, such nonlinearities corrupt encoded information, causing errors. Recently, we have engineered an effective quadrature coupling between a cavity and an ancillary qubit based on an arbitrarily weak native dispersive interaction through the use of large phase space displacements. In this talk, we extend the idea of using large displacements in a cavity’s phase space to perform universal control of a superconducting cavity with Kerr nonlinearity on the order of 1 Hz. This control will pave the way toward more sophisticated quantum error correction protocols applied to nearly linear bosonic systems. |
Wednesday, March 4, 2020 3:42PM - 4:18PM |
P16.00007: Entangling Bosonic Modes via an Engineered Exchange Interaction Invited Speaker: Yvonne Gao The realization of robust universal quantum computation with any platform ultimately requires both the coherent storage of quantum information and (at least) one entangling operation between individual elements. The use of continuous-variable bosonic modes as the quantum element is a promising route to preserve the coherence of quantum information against naturally-occurring errors. However, operations between bosonic modes can be challenging. In analogy to the exchange interaction between discrete-variable spin systems, the exponential-SWAP unitary can coherently transfer the states between two bosonic modes, regardless of the chosen encoding, realizing a deterministic entangling operation in a programmable fashion. Here, we develop an efficient circuit to implement this unitary and realize the operation in a three-dimensional circuit QED architecture. We demonstrate high-quality deterministic entanglement between two cavity modes with several different encodings. Our results provide a crucial primitive necessary for universal quantum computation using bosonic modes. |
Wednesday, March 4, 2020 4:18PM - 4:30PM |
P16.00008: The Kerr-cat qubit: efficient readout and two-qubit gates Nicholas Frattini, Alexander Grimm, Shruti Puri, Chan U Lei, Mazyar Mirrahimi, Michel H. Devoret Superpositions of two opposite-phase coherent states in an oscillator, so-called Schrödinger cat states, can encode a noise-biased qubit, meaning a qubit with a strong protection against one error channel. Such a protected "cat qubit" has the ability to significantly reduce the overhead associated with quantum error correction in, for instance, a surface-code-style architecture. This overhead reduction relies on the ability to perform all gates in a manner that preserves the noise bias. In this talk, we review our implementation for the Kerr-cat qubit, which is based on the interplay between two-photon driving and Kerr nonlinearity. This scheme is compatible with fast, high-fidelity single qubit gates and achieves a strong noise bias. We will report on experimental improvements, the efficiency of the quantum non-demolition (QND) readout of this qubit, and our progress towards the realization of a noise-biased CNOT gate between two such Kerr-cat qubits. |
Wednesday, March 4, 2020 4:30PM - 4:42PM |
P16.00009: Multiplexed photon number measurement of a cavity using the fluorescence of a coupled qubit. Antoine Essig, Quentin Ficheux, Peronnin Theau, Nathanael Pierre Cottet, Raphael Lescanne, Alain Sarlette, Pierre Rouchon, Zaki Leghtas, Benjamin Huard Measuring the photon number of an electromagnetic mode in a quantum nondemolition manner is instrumental to control the quantum state of a cavity, detect photon emission or measure work. In the microwave domain it can be done using the dispersive coupling between the cavity of interest and a coupled Rydberg atom or superconducting circuit. This method has been used successfully to count up to about a dozen photons, to realize Quantum Zeno dynamics experiments, or count photon number parity. Yet this technique has constraints on the measurement time. In particular it increases with the maximal number of photons. In this contribution, we present a technique that avoids this constraint by using the resonant fluorescence of a qubit coupled to the resonator of interest and a multiplexing measurement of the fluorescence field. We show an experiment where an independent quantum state tomography can be performed on the resonator to compare the result of the conventional method to this new technique. |
Wednesday, March 4, 2020 4:42PM - 4:54PM |
P16.00010: Full characterization and universal control of a superconducting 3D transmon qudit Xian Wu, Luis Martinez, Yaniv J Rosen, Jonathan L. DuBois While high fidelity single qubit and two-qubit gates have been realized for transmons, use of higher levels as a quantum resource has not yet been systematically studied. Coherent control of these higher energy states offers a direct route to increasing the available quantum volume of a given quantum circuit. In addition, the increasing charge dispersion present in higher level states offers a unique tool for studying charge noise. Here, we use the lowest four levels of a 3D transmon as the quantum register, qudit, which is computational equivalent to two qubits. We measure the decoherence times for each of the excited state. We also demonstrate multiplexing readout and universal control of the qudit with a single drive line. |
Wednesday, March 4, 2020 4:54PM - 5:06PM |
P16.00011: Advancements in 3D cavity fabrication and design for improved multimode quantum memories Andrew Oriani, Srivatsan Chakram, Kevin He, Alexander Anferov, Akash Dixit, John Clai Owens, David I Schuster Superconducting multimode cavities can provide a hardware efficient means for quantum information storage and processing. To increase mode density, reduce cross-talk, and increase gate fidelities, it is important to build cavities with tailored mode spacing and very long coherence times. In this talk we present advances in materials processing and design of 3D microwave resonators to increase mode lifetimes beyond that of state-of-the-art aluminum cavities. This includes moving to higher Tc superconductors and quantifying the efficacy of various surface treatment procedures in reducing dissipative loss mechanisms. In doing so we will present a pathway for developing these cavities into novel 3D multimode architectures for next-generation randomly accessible quantum memories and processors. |
Wednesday, March 4, 2020 5:06PM - 5:18PM |
P16.00012: Towards strong multi-mode coupling between a transmon and a metamaterial resonator Sagar Indrajeet, Haozhi Wang, B.L.T. Plourde, Matthew D. LaHaye, Matthew D Hutchings, Bruno Taketani, Frank Wilhelm A high density of modes can be produced using metamaterial resonant structures made from arrays of lumped circuit elements, to which a flux-tunable transmon qubit can be coupled. For such a system, we have measured the coupling strength of the qubit to multiple modes by tuning the flux and observing the splitting in the transmission of each mode. In these initial measurements, the coupling strengths were larger than the individual mode linewidths, but did not exceed the inter-mode spacing. We discuss approaches to decrease the mode spacing in this system and simulate the spectrum numerically. In addition, we discuss techniques for increasing the coupling strength between these modes and the transmon qubit. For appropriate parameters, we show that it will be to possible to reach the regime where the qubit can be coupled to multiple modes simultaneously, which will have applications in analog quantum simulations and multi-mode cQED. |
Wednesday, March 4, 2020 5:18PM - 5:30PM |
P16.00013: Observation of atom-photon bound states in a rectangular waveguide Arkady Fedorov, Pradeepkumar Nandakumar, Jose Andres Rosario Hamann, Maximilian Zanner, Martin Weides Within the stopband, where the density of states is zero, no travelling modes are allowed |
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